NES Repair Issues...

Hey guys, I'm new here to the forums. This will be my first post. I have three NES consoles that I'm trying to repair at the moment...

-One of them gives small glitches while playing Super Mario Bros(Possibly more games). I have tried four different cleaned cartridges and still get the same glitches. I removed the 72-Pin connector and cleaned the connectors on the motherboard with the cleaning paste and spray. I then installed a brand new 72-Pin connector and the issue still remains.

-One works perfectly fine, all except for the controller ports. When I turn it on with a two player game inserted, it automatically selects the two player option and then neither one of the controllers will work at all. I have tried three different controller ports installed and still get the same error.

-The last console, will simply not power on at all. I fear that the power source is dead and have no clue where to start besides buying a new motherboard.

Please give any suggestions, as they will all be helpful.

 

I would try looking around for any busted traces, sounds to me like there might be a bad trace going to one of the SRAM chips. If that's not the case then one of them might have gone bad.

Check around the controller port area for any shorts. Failing that it might be one or both of the 74HC368 chips causing the issue (those are the logic chips that handle the controller inputs).

I'm willing to bet it's a bad 7805, use a multimeter to check the voltage output on the 7805 and if it's zero that's your problem. The 7805 is a super common part so no worries about replacing it.

 

Also check the power switch, it could have gone bad as well. Good luck on the repair.

 

Would you mind posting a pic or pointing me in the right direction of the SRAM & 74HC368 chips? I'm comfortable with a little soldering if necessary, but some of this might be beyond my expertise.

 

Try boiling the 72-pin connector (provided there aren't any missing pins) for that console. Use the OEM one. 3rd party Pin connectors are crap.
http://www.nintendoage.com/forum/messageview.cfm?StartRow=1&catid=7&threadid=63483

You probably may need to clean the motherboard connector for the ZIF as well(where the 72pc goes). Check if any of the contacts are scratched to hell or anything too.

 

The SRAM chips are the ones right next to the cart connector. The 74HC368s are fairly self-explanatory as they're labeled as such; they're located close to where the controller ports plug into the motherboard.

 

Ok, I have located the chips. I'm going to crack the other two open and look for anything strange. Can the chips be tested to see if they are bad or not, like the power source issue?